and they selected a trapezoidal acceleration curve as the motion curve of the electronic shogging  syste  6‘7 They just displayed the theoretical calculation,  but the  implementing process of how to control the servo motor effectively with the curve was not given. In the paper of Mermelsteia ct aI. !’! , the method of selecting servo motors based on minimizing the power needed performing the fastest motion required for a circular warp-knitting machine had been reported. But due to the different structures between circular and flat warp-knitting machine, the motor was chosen according to whether the method could meet the response demand of the flat warp-knitting machine or not, mcanwI›iTe, the choosing procedure was too complicated. To satisfy the high-precision location of bar shogging, most of the motors which were used to perfomi overlap and underlap were designed to work in the position control mode[’  .  However, the acceleration of servo motor was shaft. Figure I shows the motion time sequence of yarfi laying shogging during one period of looping. Here the 8 is the main shin rotason degree of iiiiderlap, II is the degree of overlap, and the shadow region represents that the guide bar sto slogging when the guide needles Swilig though the groove ptaas.

Fig. 1  Lap motion of guide bar its maifl shall circle

}: jjp(}gjj p jyjjj$ . )'i};jjj(jjj;(} SGighG0 gg(} Technology SU{IpOi‘t PfO$iBIT1 , (flljflfl ( NO. 20I2BAF'13B03 Technology Guidance Program ( No. 20lltXi7) i Ji«»gnan University independent R•s•aich Funding Plan, s Correspond‹»ce sh‹›uld be ad d io ZHANG Qt , E-mail: qiqi93l B'16õ. com Industry  AssociationJIJ5RP2I1 A04) 

Journal  of  Donghua  UnivaMty ( Eng.  Ed. )   Vol. 30,  No. 3 (2013)

. 1. 2 Control conditions

Due to the mechanical layout, the front guide bar GBl has the minimum overlap degree 8, =38° in all four guide bars of Tricot HKS4 warp-knitting machine. The maximal s stop frequency  of guide bar  shogging  winning  is /p„   =6 x W8, =157. 9 Hz when the rotate speed of principle axial is n -- I OOD tmin.

For the E28HKS4 warp-knitting machine, the needle pitch L =25. 4/28 = 0. 907 mm , needle thickness of gmove pin a --0. 25 mm, thickness of guide needle b -- 0. 22 mm, let yarn clearance is d = Lz'2 - ( ii + b ) Z2 = 0. 219 mm, the iDaximal yarn distance which this machine can knit is d--0. 175 mm , and the maximal residual gap is 6p  =d —d =0. 044 mm.

For electronic shogging system of high-speed warp-knitting machine, the guide bais from 180 inch to 210 inch are constrained by the yarns , forced to reversing move at high frequency of 160 times for I s, and the position error should be less than 0. 044 mm. Therefore, the motion features can be expressed that the guide bar moves with some load inertance the reversing start?’stop at high frequency and reciprocating motion at high precision. In order to achieve the constrained goal, the electronic shogging system should choose the serro control system with smaller scanning cycle and higher response property. The acceleration and deceleration motion curves with smoothed and electronic cant control   8 * continuity also should be chosen.

2  System Design

2. 1   Control model

The servo function of alternating current dynamo ( AC motor) was controlled through three loop control models such as electric current, velocity , and position. In these control models, the torque control model had the shortest scan c)’c1e. However, the control object of motors was very difficult to get the precise position. The position control model had better precise position , but each servo circle should spend 250 ps to calculate. Therefore, the response speed of servo was very slow. The speed control model had the scan circle of 150 (cs between the toi9ue control model and the position control model. This model had good dynamic resnonse property and good precise position. Therefore, the speed control model was the best condition for servo motor to drive the guide bar.